aeslua/ciphermode.lua

local aes = require("aeslua.aes");

local util = require("aeslua.util");

local buffer = require("aeslua.buffer");

local public = {};

local aeslua = require("aeslua");

aeslua.ciphermode = public;

--

-- Encrypt strings

-- key - byte array with key

-- string - string to encrypt

-- modefunction - function for cipher mode to use

--

function public.encryptString(key, data, modeFunction)

    local iv = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

    local keySched = aes.expandEncryptionKey(key);

    local encryptedData = buffer.new();

    for i = 1, #data/16 do

        local offset = (i-1)*16 + 1;

        local byteData = {string.byte(data,offset,offset +15)};

        modeFunction(keySched, byteData, iv);

        buffer.addString(encryptedData, string.char(unpack(byteData)));    

    end

    return buffer.toString(encryptedData);

end

--

-- the following 4 functions can be used as 

-- modefunction for encryptString

--

-- Electronic code book mode encrypt function

function public.encryptECB(keySched, byteData, iv) 

	aes.encrypt(keySched, byteData, 1, byteData, 1);

end

-- Cipher block chaining mode encrypt function

function public.encryptCBC(keySched, byteData, iv) 

    util.xorIV(byteData, iv);

    aes.encrypt(keySched, byteData, 1, byteData, 1);    

    for j = 1,16 do

        iv[j] = byteData[j];

    end

end

-- Output feedback mode encrypt function

function public.encryptOFB(keySched, byteData, iv) 

    aes.encrypt(keySched, iv, 1, iv, 1);

    util.xorIV(byteData, iv);

end

-- Cipher feedback mode encrypt function

function public.encryptCFB(keySched, byteData, iv) 

    aes.encrypt(keySched, iv, 1, iv, 1);    

    util.xorIV(byteData, iv);

    for j = 1,16 do

        iv[j] = byteData[j];

    end        

end

--

-- Decrypt strings

-- key - byte array with key

-- string - string to decrypt

-- modefunction - function for cipher mode to use

--

function public.decryptString(key, data, modeFunction)

    local iv = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

    local keySched;

    if (modeFunction == public.decryptOFB or modeFunction == public.decryptCFB) then

    	keySched = aes.expandEncryptionKey(key);

   	else

   		keySched = aes.expandDecryptionKey(key);

    end

    local decryptedData = buffer.new();

    for i = 1, #data/16 do

        local offset = (i-1)*16 + 1;

        local byteData = {string.byte(data,offset,offset +15)};

		iv = modeFunction(keySched, byteData, iv);

        buffer.addString(decryptedData, string.char(unpack(byteData)));

    end

    return buffer.toString(decryptedData);    

end

--

-- the following 4 functions can be used as 

-- modefunction for decryptString

--

-- Electronic code book mode decrypt function

function public.decryptECB(keySched, byteData, iv) 

    aes.decrypt(keySched, byteData, 1, byteData, 1);

    return iv;

end

-- Cipher block chaining mode decrypt function

function public.decryptCBC(keySched, byteData, iv) 

	local nextIV = {};

    for j = 1,16 do

        nextIV[j] = byteData[j];

    end

    aes.decrypt(keySched, byteData, 1, byteData, 1);    

    util.xorIV(byteData, iv);

	return nextIV;

end

-- Output feedback mode decrypt function

function public.decryptOFB(keySched, byteData, iv) 

    aes.encrypt(keySched, iv, 1, iv, 1);

    util.xorIV(byteData, iv);

    return iv;

end

-- Cipher feedback mode decrypt function

function public.decryptCFB(keySched, byteData, iv) 

    local nextIV = {};

    for j = 1,16 do

        nextIV[j] = byteData[j];

    end

    aes.encrypt(keySched, iv, 1, iv, 1);

    util.xorIV(byteData, iv);

    return nextIV;

end

return public;